1. Field of the Invention
This invention relates to apparatus for detecting the presence of, and actuating the feeding of sheets of paper in paper folding machines and the like.
2. Description of the Prior Art
In paper folding and other like machines it is important that the stack of paper be fed uniformly to the location where the individual sheets are removed from the stack or load, and then individually folded or creased. Paper sheets due to atmospheric or other conditions can easily stick together, curl up and jam the machine if the stack is advanced too fast, and if the stack is not advanced fast enough, time is wasted and unnecessary expense results. Most paper folding machines use a micro-switch with a protruding arm, that is engaged by the stack of paper, and signals the feeder to advance the paper for folding but such devices are not precise in operation. Should the edge of the paper curl up and not engage the arm, then the paper stack will over-feed and the stack will jam the machine. Should the paper edge curl down, the switch arm will be contacted and cause the sheet to be distorted. The difficulties encountered with available mechanical devices requires the operators constant attention to the machine, and increases the cost to the customer.
Other devices have been proposed, such as shown in Motokawa Japanese Pat. No. 161,243 wherein a device is provided to prevent the improper feeding of two or more pieces of paper in a printing machine. The Motokawa device requires that the sheets of paper pass over a light emitting device with a detector on the other or receiving side, and which quantity of light penetrating the paper sheets is determined and compared to a memory value and if lower, then paper feeding is stopped and the machine cleared. This device does not detect the presence of the load of paper like that of my invention, is not suitable for opaque paper and suffers from other problems.
The U.S. Pat. to Brown No. 3,495,089 discloses alignment sensing devices which utilize light-emitting semi-conductors. The device is used for web edge aligning and includes a light-emissive semi-conductive device which is stimulated to emit radiation of a predetermined spectral characteristic along a sensing path, and with a radiation sensing structure above it, which receives the radiation, and provides a sensing output in accordance with the detected variations of the web or other structure, which variations affect the radiation path. No structure which is self contained and detects the presence of a load of paper is provided, in Brown nor would Brown be suitable for use in paper folding machines.
Similar devices where a light path is broken are shown in the U.S. Pat. to Jefree No. 3,906,240 and Martin No. 3,617,759 but they do not sense the presence of a load of paper, as is accomplished by my device and are not suitable for use in paper folding machines.
The device of my invention does not touch the load or stack of paper, does not require the breaking of a beam of energy with emitters and detectors between which objects must pass, and is suitable for providing precision control of paper feeding for paper folding machines and the like.